OS hardening and security best practices in Operating Systems - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to identify the primary goal of OS hardening.

Operating Systems

The main purpose of OS hardening is to [1] the system against attacks.

Drag options to blanks, or click blank then click option'

Aprotect

Bignore

Cslow down

Dcomplicate

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'ignore' or 'slow down' as they do not improve security.

OS hardening means making the system more secure by protecting it from attacks.

2fill in blank

medium

Complete the code to name a common OS hardening practice.

Operating Systems

One common OS hardening step is to [1] unnecessary services.

Drag options to blanks, or click blank then click option'

Adisable

Bignore

Cupdate

Dinstall

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'install' or 'ignore' which do not reduce risks.

Disabling unnecessary services reduces the attack surface of the system.

3fill in blank

hard

Fix the error in the statement about password policies.

Operating Systems

Strong password policies require users to [1] passwords regularly.

Drag options to blanks, or click blank then click option'

Areuse

Bchange

Cshare

Dforget

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'reuse' or 'share' which reduce security.

Changing passwords regularly helps prevent unauthorized access.

4fill in blank

hard

Fill both blanks to complete the best practice for firewall configuration.

Operating Systems

A good firewall setup [1] all incoming traffic by default and [2] only trusted connections.

Drag options to blanks, or click blank then click option'

Ablocks

Ballows

Cignores

Dmonitors

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing 'ignores' or 'monitors' which do not actively block traffic.

Firewalls should block all incoming traffic by default and allow only trusted connections to improve security.

5fill in blank

hard

Fill all three blanks to complete the dictionary comprehension for checking system updates.

Operating Systems

updates = { [1]: [2] for [3] in installed_packages if packages[[3]] == 'outdated' }

Drag options to blanks, or click blank then click option'

Apkg

Bpkg_version

Dinstalled_packages

Attempts:

3 left

💡 Hint

Common Mistakes

Using the wrong variable names or missing the condition.

This comprehension creates a dictionary of package names and their versions for packages marked as outdated.

Practice

1. What is the main goal of OS hardening in computer systems?

easy

A. To increase the number of installed applications

B. To reduce security vulnerabilities by tightening system settings

C. To make the system run faster by removing hardware

D. To allow all users full access to system files

Solution

1. Step 1: Understand OS hardening purpose

   OS hardening means making the system more secure by reducing weak points.

2. Step 2: Evaluate options

   Only To reduce security vulnerabilities by tightening system settings describes reducing vulnerabilities by tightening settings, which matches OS hardening.

3. Final Answer:

   To reduce security vulnerabilities by tightening system settings -> Option B

4. Quick Check:

   OS hardening = reduce vulnerabilities [OK]

Hint: OS hardening means making system safer, not faster or more open [OK]

Common Mistakes:

• Confusing hardening with performance tuning
• Thinking hardening means adding more software
• Believing hardening allows more user access

2. Which of the following commands is commonly used to update software packages on a Linux system as part of OS hardening?

easy

A. apt-get update

B. rm -rf /

C. mkdir new_folder

D. ping google.com

Solution

1. Step 1: Identify update command

   On Linux, apt-get update refreshes package lists to get latest software versions.

2. Step 2: Check other commands

   rm -rf / deletes files dangerously, mkdir creates folders, ping tests network. Only apt-get update updates software.

3. Final Answer:

   apt-get update -> Option A

4. Quick Check:

   Update packages = apt-get update [OK]

Hint: Updating software uses package manager commands like apt-get update [OK]

Common Mistakes:

• Confusing file commands with update commands
• Using network commands for updating
• Not knowing package manager syntax

3. Consider this Linux command sequence for OS hardening:

sudo apt-get update && sudo apt-get upgrade -y

What is the expected result after running these commands?

medium

A. The system will remove all unused files

B. The system will restart immediately

C. The system will create a backup of all files

D. The system will update package lists and upgrade installed packages automatically

Solution

1. Step 1: Analyze apt-get update

   This command refreshes the list of available software packages and versions.

2. Step 2: Analyze apt-get upgrade -y

   This command upgrades all installed packages to the latest versions automatically without asking for confirmation.

3. Final Answer:

   The system will update package lists and upgrade installed packages automatically -> Option D

4. Quick Check:

   Update + upgrade = refresh + install latest [OK]

Hint: Update refreshes lists; upgrade installs new versions [OK]

Common Mistakes:

• Thinking upgrade deletes files
• Assuming commands create backups
• Believing system restarts automatically

4. A system administrator tries to disable unused services for OS hardening using this command:

systemctl disable sshd

But the SSH service still starts after reboot. What is the likely mistake?

medium

A. They forgot to mask the service with systemctl mask sshd

B. They should use systemctl stop sshd to stop the service immediately

C. They need to reboot twice for changes to apply

D. The service name is incorrect; it should be ssh instead of sshd

Solution

1. Step 1: Understand systemctl disable effect

   This command prevents the service from starting automatically but does not stop it if already running or mask it.

2. Step 2: Recognize masking necessity

   Masking a service with systemctl mask blocks all attempts to start it, including manual or dependency starts.

3. Final Answer:

   They forgot to mask the service with systemctl mask sshd -> Option A

4. Quick Check:

   Disable ≠ block start; mask blocks start [OK]

Hint: Disable stops auto-start; mask blocks all starts [OK]

Common Mistakes:

• Confusing disable with stop
• Not knowing mask blocks service fully
• Assuming reboot applies all changes immediately

5. You want to harden a Linux server by removing unnecessary user accounts and setting strong password policies. Which combination of actions best achieves this?

hard

A. Keep all default accounts and disable system updates to avoid changes

B. Create new user accounts with simple passwords and disable firewall

C. Delete unused user accounts, enforce password complexity via PAM modules, and set account lockout policies

D. Allow all users to use root privileges and disable password expiration

Solution

1. Step 1: Remove unused user accounts

   Unused accounts increase attack surface; deleting them reduces risk.

2. Step 2: Enforce strong password policies

   Using PAM modules to require complexity and setting lockout policies prevents easy guessing and brute force attacks.

3. Final Answer:

   Delete unused user accounts, enforce password complexity via PAM modules, and set account lockout policies -> Option C

4. Quick Check:

   Remove unused + strong passwords = better security [OK]

Hint: Remove unused accounts and enforce strong passwords [OK]

Common Mistakes:

• Creating weak passwords intentionally
• Allowing root access to all users
• Disabling updates or firewalls